Mike Westfall WDX6O wrote:

Brenda Ann Dyer wrote:
"John Byrns" wrote in message
...

The term "local stations" as used above has also been used recently in
several other threads. I am curious what the readers of this forum would
consider to be a "local station"?


I have no idea what they use to describe them now...

The local "graveyard" stations are on 1230, 1240, 1340, 1400, 1450 and
1490. Nearly all are 1000 Watts day and night.

--
Mike Westfall, N6KUY, WDX6O


Yep, ye olde "local channel" stations as they used to call them. If
you lived on top of one, it was fine in the daytime. But anywhere in
the USA I've ever been, those frequencies are hash at night.

What defines "local stations" in a practical "everyday" sense as far
as reception goes is a good question. I think everyone would have their
own definition of that. I would confine it to mean stations clearly
receiveable, at or near full modulation, in the *daytime*. With a good
MW receiver and antenna, many, many stations become, in effect, "local"
stations at night, especially in the wintertime.

When I was growing up in Detroit 40 years ago, the two most distant
stations that came in clearly, if dimly (but no fade or distortion) were
in Marine City, MI (50 miles away) a 5,000W station, and Saline, MI (33
miles away) a one or two thousand watt station, best as I recall. That
was daytime listening. At night, WBZ from Boston was easy listening,
night after night, but would hardly qualify as a "local" station to the
Detroit area. The magic of nightime is was hooked me on DX in the first
place.

Yeah, good "bull session" question.

Tony

In article ,
(John Byrns) wrote:

In article , Patrick Turner
wrote:

John,

You seem to be limiting your considerations to the 'tangential clipping'
and not to other distortions that will occur.

On the contrary I alluded to the other problems in my post above where I
said "while the traditional RC circuit has its problems". The problem is
that Patrick has a very thick head, so I am trying to keep things simple
so he might get the point.

Oh, thank God the dueling banjos of rec.audio.tubes are back with more
of their lethally boring detector talk.

You don't often have a Troll this technical although it is getting more
goofy by the post.

--
Telamon
Ventura, California

John Byrns wrote:

In article , Patrick Turner
wrote:

John,

You seem to be limiting your considerations to the 'tangential clipping'
and not to other distortions that will occur.

On the contrary I alluded to the other problems in my post above where I
said "while the traditional RC circuit has its problems". The problem is
that Patrick has a very thick head, so I am trying to keep things simple
so he might get the point.

Unfortunately, you have not yet done a proper comparison measurement
of a traditional detector driven off an IFT secondary, and compared
the results to what I have proposed and posted using two CF tubes.

I'm not sure what "proper comparison measurements", or "CF tubes", have to
do with the theoretical aspects of tangential clipping?

It means to build samples of two comparable circuits, and
thoroughly measure and observe the workings of each,
and make your conclusions.

That isn't too hard now surely?

Unfortunately I
don't possess an AM generator that is adequate for making these
measurements, that is a generator that will do 100% negative modulation,
or anywhere near it, with low distortion. It isn't clear that you possess
such a generator either, and you seem to have engaged in a certain amount
of shucking and jiving with respect to the actual performance of your
detector.

I have two such generators, a old Topward, which uses chips to easily get
100% modulation of any signal between 2 Hz and 2 Mhz with a 400 Hz tone.

The other is a tube one I built, which is also capable of 100% modulation,
but the thd in the AF envelope is around 3% at the onset of 100% modulation.



Why don't you describe the AM generator you are using, how close it gets
to 100%, and what the distortion is at that point? I know you are using a
CRO to check for distortion, rather than a distortion analyzer, but still
if the generator has serious distortion at the extremes of modulation it
could mask some of the faults in a detector.

If you have a dual trace CRO, you should be able to view the
input gene RF signal on one trace, and the recovered audio from the detector
on the other trace.

Each trace can be overlaid, and at low % of modulation, the recovered
audio trace should perfectly outline the input RF signal modulation,
so if there is any thd in the input modulation shape, it doesn't matter.
The two traces should remain locked close when the amplitude of
the input RF and or modulation % is increased at least to an equivalent
level of signal to a strong local station when its received using 10 metres of
wire
as an antenna, and perhaps -8 volts of AGC is being generated.



I don't have the time to spend on discussions that get nowhere with
someone who hasn't the time to connect a handful of parts on a bench, and
do some real work, instead of endlessly talking around the subject,

I am working on such a project, but first I must solve the AM generator
problem. I am beginning to get an idea or two as to how I can overcome
the AM generator problem. You have nearly pushed me to the point of
action in my workshop, as Danger Dave did a few years back with respect to
the workability of an amplifier design I had been contemplating for
several years. Once I built it, Danger Dave was quickly proved to be full
of it, and I expect a similar result again, once you have motivated me
sufficiently. But first lets hear more about the AM generator you are
using for your tests?

Its a simple triode oscillator with a grid LC, with tap on the LC for the cathode
current.

This feeds a 6BX6 RF amp, which has an LC in its anode circuit.

The AF is fed into the 6BX6 grid circuit to alter the anode current at AF, and
modulate the output at the anode.
The anode LC has a secondary winding to reduce the output impedance.

One two gang tuning cap from an old radio is used.

It took about a fortnight to build, and a fortnight to de-bug, and to get the
sawtooth oscillator working, so when switched to 455 kHz,
the Fo could be wobulated 40 kHz each side to display the IF bandpass contour.

I used about 10 x 68v zener diodes operating at a DV lower than the zener voltage
to make a varicap diode to give a high enough C shift to cause the wanted F
deviation.
Some wobulators use a spinning tuning cap driven by a motor, but I wanted
no mechanical parts which could wear out.

and making incorrect statements about skull bone thickness.

The process taught me all about my own cerebral bone thickness.
I took aim as to what I wanted from thre test gear, and I didn't stop
until I achieved it.

Probably just as well I never had any involvement with discussion groups
back in 1993 to 2000, I was learning by doing, and I wasn't able to load all my
dumb
questions, about 20 per day, onto any news group.

I answered many questions myself.




As they say, "if the shoe fits wear it"! I remember the "thick as a
brick" thread from earlier this year, where you clearly demonstrated the
thickness of your skull. For those don't remember, that adventure might
have been called the "octave" matter. It was related to the slope of the
attenuation curve of an RF tank circuit, IFT, or other similar circuit.

Phil Allison and I were quite correct in our assessment about
attenuation rates in RF tank circuits, and I was the one to measure a typical
LC taken from an old radio and post the results at the binaries groups,
to prove and define what I was saying, leaving no room for any doubt, or BS.


Workshops, simulations, and what not didn't enter into the matter because
you had conveniently measured, plotted, and posted the response curves for
an AM aerial circuit which made a perfect example for discussion. The
trouble started when you and your fellow countryman Phil Allison claimed
that the slope of the attenuation curve of a tank circuit was stepper
close to resonance and that the slope of the attenuation progressively
became less steep as you moved away resonance.

Well indeed the rate of attenuation is steeper near Fo, and then becomes less.

There is only 6 dB /octave attenuation when you are 20 dB or more away from Fo.
Say you have a tuned LC with Fo = 1,200 kHz, then at 600 kHz, the rate of
attenuation
is 6 dB /octave, so that between 600 kZ and 300 kHz, there is only 6 dB of
attenuation.

But close to Fo, within a few kHz, and if the Q of the LC is say 50,
the rate of attenuation is far far greater than 6 dB / octave with regard to RF
frequencies.
The rate of audio F carried by a modulated carrier follows the RF attenuation
shape.


I had been under the
impression that the slope of the attenuation curve actually increased as
you moved away from resonance, and asymptotically approached a slope
determined by the order of the filter. After a few back and forths it
became obvious to me that the problem was one of the different frequency
reference points we were using, you and Phil were using Zero frequency as
your reference, while I was using the center frequency of the filter as my
reference. At that point I said I completely agreed with your
conclusions, given your frame of reference, but you refused to accept my
concept of using the filter center frequency as an alternative view of the
situation, and told me it just wasn't valid. That is a perfect example of
a thick skull, since generally there are alternate definitions for things,
and as long as they are consistent with the facts, in that case your
measured and posted results, they are just as valid as what you may
consider to be a more conventional viewpoint, although in the case of the
"octave" matter I am not entirely sure yours was the conventional
viewpoint, but the bottom line was they both worked, and you denied that
my approach had validity.

I have seen no reference of your interpretive methodology in any text books,
and the text book methods to which I adhere to explain it all nicely,
and I don't have any intention of going right through all that long and tortuous
discussion again.
I been there, done that, and I have moved on.

Meanwhile, I am probably wasting far too much time as it is re-building an
old Stromberg Carlson, giving it a real good Turnerization, with singing lessons
included.

But slowly the work looks promising....

It will never be as good as my other radio circuit which I posted last week
because
the IF tube is a vari mu 6G8, and I have AGC applied......


Patrick Turner.




Regards,

John Byrns

Surf my web pages at, http://users.rcn.com/jbyrns/

Oh, thank God the dueling banjos of rec.audio.tubes are back with more
of their lethally boring detector talk.

You don't often have a Troll this technical although it is getting more
goofy by the post.


Not a complete troll, as we are attempting to figure out a way to
get decent sound reception from AM radio stations. We believe that it
can be done, and we're hashing out the details. And adding a bit of
flame war spice to liven things up... ;-)

In article , Patrick Turner
wrote:

John Byrns wrote:

In article , Patrick Turner
wrote:

John,

You seem to be limiting your considerations to the 'tangential
clipping'
and not to other distortions that will occur.

On the contrary I alluded to the other problems in my post above where I
said "while the traditional RC circuit has its problems". The
problem is
that Patrick has a very thick head, so I am trying to keep things simple
so he might get the point.

Unfortunately, you have not yet done a proper comparison measurement
of a traditional detector driven off an IFT secondary, and compared
the results to what I have proposed and posted using two CF tubes.

I'm not sure what "proper comparison measurements", or "CF tubes", have to
do with the theoretical aspects of tangential clipping?

It means to build samples of two comparable circuits, and
thoroughly measure and observe the workings of each,
and make your conclusions.

That isn't too hard now surely?

That is not responsive to my question as asked, and I am not talking about
answering a question with a question.

Unfortunately I
don't possess an AM generator that is adequate for making these
measurements, that is a generator that will do 100% negative modulation,
or anywhere near it, with low distortion. It isn't clear that you possess
such a generator either, and you seem to have engaged in a certain amount
of shucking and jiving with respect to the actual performance of your
detector.

I have two such generators, a old Topward, which uses chips to easily get
100% modulation of any signal between 2 Hz and 2 Mhz with a 400 Hz tone.

Is "2 Hz" a typo? If not the resulting wave form at 100% modulation with
a 400 Hz tone would be interesting to observe on the CRO. Do you know
what the distortion for this "old Topward" is at 100% modulation? It
would be nice to be able to get away form subjective CRO measurements and
use a distortion analyzer instead.

The other is a tube one I built, which is also capable of 100% modulation,
but the thd in the AF envelope is around 3% at the onset of 100% modulation.

Its a simple triode oscillator with a grid LC, with tap on the LC for
the cathode
current.

This feeds a 6BX6 RF amp, which has an LC in its anode circuit.

The AF is fed into the 6BX6 grid circuit to alter the anode current at AF, and
modulate the output at the anode.
The anode LC has a secondary winding to reduce the output impedance.

One two gang tuning cap from an old radio is used.

It took about a fortnight to build, and a fortnight to de-bug, and to get the
sawtooth oscillator working, so when switched to 455 kHz,
the Fo could be wobulated 40 kHz each side to display the IF bandpass contour.

I used about 10 x 68v zener diodes operating at a DV lower than the
zener voltage
to make a varicap diode to give a high enough C shift to cause the wanted F
deviation.
Some wobulators use a spinning tuning cap driven by a motor, but I wanted
no mechanical parts which could wear out.

Thanks for the description of your AM generator, or AM/FM generator as it
sounds like it actually is.


As they say, "if the shoe fits wear it"! I remember the "thick as a
brick" thread from earlier this year, where you clearly demonstrated the
thickness of your skull. For those don't remember, that adventure might
have been called the "octave" matter. It was related to the slope of the
attenuation curve of an RF tank circuit, IFT, or other similar circuit.

Phil Allison and I were quite correct in our assessment about
attenuation rates in RF tank circuits, and I was the one to measure a typical
LC taken from an old radio and post the results at the binaries groups,
to prove and define what I was saying, leaving no room for any doubt, or BS.

But that was my point, you were quite correct using your frame of
reference, on the other hand my assessment of the attenuation rates in RF
tank circuits was also correct, and also perfectly described your measured
data, even though it used a different frame of reference. Your position
was, and still seems to be that anyone who takes a different perspective
on a matter is of necessity wrong, even if the alternate perspective
explains the data as well, or even better than your perspective does, you
need to learn to think outside the box, and be more creative as it were.

Workshops, simulations, and what not didn't enter into the matter because
you had conveniently measured, plotted, and posted the response curves for
an AM aerial circuit which made a perfect example for discussion. The
trouble started when you and your fellow countryman Phil Allison claimed
that the slope of the attenuation curve of a tank circuit was stepper
close to resonance and that the slope of the attenuation progressively
became less steep as you moved away resonance.

Well indeed the rate of attenuation is steeper near Fo, and then becomes less.

There is only 6 dB /octave attenuation when you are 20 dB or more away
from Fo.
Say you have a tuned LC with Fo = 1,200 kHz, then at 600 kHz, the rate of
attenuation
is 6 dB /octave, so that between 600 kZ and 300 kHz, there is only 6 dB of
attenuation.

But close to Fo, within a few kHz, and if the Q of the LC is say 50,
the rate of attenuation is far far greater than 6 dB / octave with
regard to RF
frequencies.

Again that is one perspective, but it doesn't mean there aren't over
equally valid perspectives, all that matters is that a view correctly
describes the measured data, which mine does, and IIRC yours does also.

The rate of audio F carried by a modulated carrier follows the RF attenuation
shape.

This statement is a little ambiguous, could you clarify it? It almost
sounds like you are claiming the rate of attenuation of the audio
recovered from a single tuned tank circuit will be greater than 6dB/Octave
near the corner frequency? Well actually now that I think about it that
probably is what you are trying to say.

I had been under the
impression that the slope of the attenuation curve actually increased as
you moved away from resonance, and asymptotically approached a slope
determined by the order of the filter. After a few back and forths it
became obvious to me that the problem was one of the different frequency
reference points we were using, you and Phil were using Zero frequency as
your reference, while I was using the center frequency of the filter as my
reference. At that point I said I completely agreed with your
conclusions, given your frame of reference, but you refused to accept my
concept of using the filter center frequency as an alternative view of the
situation, and told me it just wasn't valid. That is a perfect example of
a thick skull, since generally there are alternate definitions for things,
and as long as they are consistent with the facts, in that case your
measured and posted results, they are just as valid as what you may
consider to be a more conventional viewpoint, although in the case of the
"octave" matter I am not entirely sure yours was the conventional
viewpoint, but the bottom line was they both worked, and you denied that
my approach had validity.

I have seen no reference of your interpretive methodology in any text books,
and the text book methods to which I adhere to explain it all nicely,
and I don't have any intention of going right through all that long and
tortuous
discussion again.

And I wouldn't ask you to, if you notice I am not disputing your method, I
am simply disputing your apparent claim that my method is invalid. I
would ask you for one favor though, could you cite some of the textbooks
that explain your method so nicely? I have suddenly realized that in the
previous furor that you and Phil raised about my method not being in
textbooks, no one asked if your method was actually presented in any
textbooks, and I have suddenly realized that I have never seen it in a
textbook, although that certainly doesn't mean it isn't. Does the RDH4
describe your method? As far as my method not being in text books, I
think that notion was thoroughly debunked in the earlier thread when both
myself and another poster provided references to textbooks that explained
my method. In fact my method is the basis of several filter design
techniques. I suspect the problem is that you are restricting your
reading to radio design textbooks, when you should perhaps be looking in
filter design textbooks for this information, which is where you can
easily find it. I don't remember seeing your method explained in any
radio design textbooks, and I have a whole shelf full, but that doesn't
mean it isn't in one somewhere because I certainly haven't read every page
of each one, and that is why I asked for a citation, so that I can become
more familiar with your approach. My reaction to your approach is the
same as yours to mine, namely assuming it is equally valid, it does not
appear to have any practical application, and tends to confuse the issue
of what is really going on.


Regards,

John Byrns


Surf my web pages at, http://users.rcn.com/jbyrns/

"Robert Casey" wrote in message
...


Not a complete troll, as we are attempting to figure out a way to
get decent sound reception from AM radio stations.

I know it's subjective, but I think most AM radios sound decent. Some sound
even better. Authoritative sources say the distortion of the typical diode
detector is under 2%, which makes sense. There's been some unsupported
ideas posted on rec.radio.shortwave that diode detectors normally have much
higher distortion levels.

Most of my radios are tube radios. Many transistor radios sound horrible on
AM. I tend to think poor AM audio from transistor radios is caused by
running the diode detector at low voltages into a low impedance load, but
I've never checked it out.


We believe that it
can be done, and we're hashing out the details.

Yeah, but how much distortion do we get from transmitter modulation?
Selective fading? A zero distortion AM detector may not be a hell of alot
better than a properly designed diode detector.

And adding a bit of
flame war spice to liven things up... ;-)


Godwin got it wrong. Threads can go on indefinitely without mentioning
Nazis. But if they run long they will get personal.

Frank Dresser

In article , Patrick Turner
wrote:

John Byrns wrote:

In article , Patrick Turner
wrote:

John Byrns wrote:

As they say, "if the shoe fits wear it"! I remember the "thick as a
brick" thread from earlier this year, where you clearly demonstrated the
thickness of your skull. For those don't remember, that adventure might
have been called the "octave" matter. It was related to the slope
of the
attenuation curve of an RF tank circuit, IFT, or other similar circuit.

Phil Allison and I were quite correct in our assessment about
attenuation rates in RF tank circuits, and I was the one to measure
a typical
LC taken from an old radio and post the results at the binaries groups,
to prove and define what I was saying, leaving no room for any
doubt, or BS.

But that was my point, you were quite correct using your frame of
reference, on the other hand my assessment of the attenuation rates in RF
tank circuits was also correct, and also perfectly described your measured
data, even though it used a different frame of reference. Your position
was, and still seems to be that anyone who takes a different perspective
on a matter is of necessity wrong, even if the alternate perspective
explains the data as well, or even better than your perspective does, you
need to learn to think outside the box, and be more creative as it were.

No, not wrong. You could be right. I simply didn't bother to disprove
what you were
saying,
since could se no need. I already had a system which works for me,
and its found in the text books.

Where is your method also found in texbooks?

You should be able to locate it with Google, back around January of this
year, if you can't find it I will post a reference again if you do me the
courtesy of citing a textbook, with page number, where a description of
your system can be found. Is it in the RDH4, what page number?

I have seen no reference of your interpretive methodology in any
text books,
and the text book methods to which I adhere to explain it all nicely,
and I don't have any intention of going right through all that long and
tortuous
discussion again.

And I wouldn't ask you to, if you notice I am not disputing your method, I
am simply disputing your apparent claim that my method is invalid. I
would ask you for one favor though, could you cite some of the textbooks
that explain your method so nicely?

I would have a dozen on my shelf which explain radio theory sufficiently well,
including RDH4, and 11 others.

Ahh, the old weapons of mass destruction excuse, you have the RDH4 and 11
other text books, and yet you can't come up with a citation for your
method?


Regards,

John Byrns


Surf my web pages at, http://users.rcn.com/jbyrns/

John Byrns wrote:

In article , Patrick Turner
wrote:

John Byrns wrote:

In article , Patrick Turner
wrote:

John Byrns wrote:

As they say, "if the shoe fits wear it"! I remember the "thick as a
brick" thread from earlier this year, where you clearly demonstrated the
thickness of your skull. For those don't remember, that adventure might
have been called the "octave" matter. It was related to the slope
of the
attenuation curve of an RF tank circuit, IFT, or other similar circuit.

Phil Allison and I were quite correct in our assessment about
attenuation rates in RF tank circuits, and I was the one to measure
a typical
LC taken from an old radio and post the results at the binaries groups,
to prove and define what I was saying, leaving no room for any
doubt, or BS.

But that was my point, you were quite correct using your frame of
reference, on the other hand my assessment of the attenuation rates in RF
tank circuits was also correct, and also perfectly described your measured
data, even though it used a different frame of reference. Your position
was, and still seems to be that anyone who takes a different perspective
on a matter is of necessity wrong, even if the alternate perspective
explains the data as well, or even better than your perspective does, you
need to learn to think outside the box, and be more creative as it were.

No, not wrong. You could be right. I simply didn't bother to disprove
what you were
saying,
since could se no need. I already had a system which works for me,
and its found in the text books.

Where is your method also found in texbooks?

You should be able to locate it with Google, back around January of this
year, if you can't find it I will post a reference again if you do me the
courtesy of citing a textbook, with page number, where a description of
your system can be found. Is it in the RDH4, what page number?

I have seen no reference of your interpretive methodology in any
text books,
and the text book methods to which I adhere to explain it all nicely,
and I don't have any intention of going right through all that long and
tortuous
discussion again.

And I wouldn't ask you to, if you notice I am not disputing your method, I
am simply disputing your apparent claim that my method is invalid. I
would ask you for one favor though, could you cite some of the textbooks
that explain your method so nicely?

I would have a dozen on my shelf which explain radio theory sufficiently well,
including RDH4, and 11 others.

Ahh, the old weapons of mass destruction excuse, you have the RDH4 and 11
other text books, and yet you can't come up with a citation for your
method?

I won't have the same books as you have, but apart from RDH4,
I have Terman's Radio Engineering,
about 6 different dated copies of ARRL,
The british Communications Handbook, 5th Ed,
Phillips Radio Paractice, Essentials of Radio by Sluurzberb&Osterfield,
Applied Electronics by the staff of the Dept of Massacgusets insitute of Technology,

Electrical and Electronic Engineering by John D Ryder,
and I am too lazy to copy out the titles of the other approximate 10 books I have
read
on old fashioned electronics which all describe filters the same way, but not the
way you do.

If you wanna uphold your methods, go write a book.

All the books backing up what I am saying are on the shelves for you to read.

Patrick Turner.



Regards,

John Byrns

Surf my web pages at, http://users.rcn.com/jbyrns/

I finally got the revised Stromberg Carlson radio tuner section running about as
well as it ever will.

It includes the dual cathode follower stage for which I posted a schematic at abse and
abpr last week.

The only changes I made was to use IN914 diodes, and 200pF and 1M for the audio RC
peak&hold
network, as well as use a 12AT7 for the CF parts.

The idle DV at the cathode of V1 is at +48 v without a carrier, but
with a test signal carrier a little larger than the strongest station here,
The DV at the C after D1 was +103v, indicating a carrier of
55 pk volts, and the audio at 400 Hz at 90% modulation was 36 vrms, or
51v pk.

I measured the thd with a 1 kHz low distortion af signal,
and got 3% at this level of signal, which is about 2 dB short of total
overload if the IF amp.
At 30% modulation, thd was about 0.2%.

Then when I reduced the RF input by 30 dB, the audio output and carrier level
all fell by 10 dB, due to AGC action, and remeasured and got the same thd figures.

The distortion is so low in the receiver including the detector that its thd
cannot be measured because it is dominated by the thd in the RF test gene,
which measures similarly when I measured it alone.

The RF gene can achieve about 96% mod but the thd becomes quite high at about 7%,
because the pentode RF tube used does not cut off at a linear rate, and
I really should have used a pair of PP tubes with a NFB loop to make the RF modulated
signal
have far less thd in the AF envelope shape.

So the conclusion is that the radio I have just got running
does not produce the buckets of thd like so many other radios I have tested,
and anyone is welcome to use the design I had in my posted schematic.

It was of some importance to get the AGC application correct.
Too much directly applied AGC will virtually cut off the IF vari mu pentode IF amp,
so that with 28vrms of audio from as big a carrier which will support that,
you may only have 0.5 mA of anode current, and when you plot
the load line, it just isn't quite right.
Better to make sure that with extreme levels of carrier, the anode current is
over 1.5 mA, and thd I expect is a little lower.

For lower levels of carrier, tube current will increase to a max of 5 mA
at no carrier at all.
There should be some method of applying at least about -1.5 v to IF and mixer tube grids
because
such tubes go a bit beserko when biased close to 0V.

I have the AGC generated by a 33pF from the V1 cathode taken to a IN914 with its cathode
grounded.
The negative voltage generated at the anode of the diode goes to a 0.05 uF via 2.2M
for the IF amp G1, and then 1M to another 0.05 to the G1 of the mixer, then 2.2M to
the -1.5v from a back bias R in the PSU.
Anyway, it works OK, and lots of other value changes didn't seem to work as well.

Audio bw was 7 kHz.
Both IFTs had their coils moved closer together, just short of causing a twin peaked
response.
After moving them and testing them in their cans, and connecting
the right value of fixed capacitance to each coil to allow the easy adjustment of the
adjust caps for 455 kHz, I rewaxed the coils in a vat.

I really don't like this type of IFT, with a ceramic base bolted to the top of a 60mm
dia al can
which is difficult to quickly inspect and modify,
and which were a complete pita to work on, but my patience paid off,
and the set was easy and reliable to align, for a symetrical attenuation slope
each side of 455 kHz.

Each of the four LC circuit are loaded with 150k, and loading with 100k
would be quite acceptable, and probably give an audio bw of 8 kHz instead of the 7 kHz.

The second CF cathode has a 39 k load to 0V, with about 2.2 mA of Ik at high levels of
carrier, and perhaps 1.2 mA at low levels.
The higher the carrier, the higher the CF idle current, which assures their linear
operation
with increasing carrier and audio output signal.

The audio is fed from CF2 cathode via 0.1 uF cap to 100k which is in series with a 100k
log volume pot.
A 390 pF across the fixed 100k slightly compensates the audio bw.

A tone baxandal passive 100k linear tone control pot will be fitted to give about
a further 5 dB treble boost or 6 dB cut at 3.4 kHz, necessary, because nearly all the
radio stations have compressed and quite bright sounding programme material,
and the mobile phone interviews and over compressed programmes are too bright.

Its quite a nice sounding tuner when connected to a 25 watt UL amp and one of my monitor

speakers in the workshop, which are well revised old Kefs, but nevertheless quite
revealing.
Bass respons eof the tuner is down to around 8 Hz due to the 0.1 uF and 200k AC load on
the output
of the second CF, which is direct coupled to the first CF, since there is no AC couple
load.

The 1M plus 200 pF could be altered to to 1M and 50 pF, which would increase the
ripple voltage about 4 times, but it will still stay substantially the same value with
audio
output signal of say 10vrms, when a low length wire antenna is used.
But the discharge rate of the 50 pF will be four times faster and the onset of
slew rate limiting will occur at a higher F and output voltage, the cost being
slightly lower detector efficiency.
The low pass ripple RC filter of 100k and 39 pF following the peak and hold 200pF and 1M

has a pole above 40 kHz so the attenuation at 45 kHz is around 22 dB,
and the level of RF finding its way into the audio amp and to the speaker would be
negligible,
and not cause any problems.
But folks could use a pair of 100k to feed the second CF, and have a pair of 39 pF caps
arranged in a feedback filter on the CF giving twice the attenuation of RF ripple.

It would be possible to construct one's own IFTs, with separate coils to be distance
adjusted, but
to get the required Q without ferrite cores which are hard for the diyer to make and
fit,
seven core fine litz wire is needed, and when one buys any of that today I don't know.
Its a pita to work with, since tinning each fine strand is difficult.
And when winding a coil, the traversing has to be done back and forth with a special
guided winder,
which hardly anyone would have, so they must make a lathe to generate the final wind up
which gives low self capacitance, and they must also have a method of makng the wound
wires adhere
to each other as the winding is done, ie, some sort of varnish.

Temperatures have fallen to around -5C and nights are a bit chilly even with a heater in
the shed;
it merely generates a cool breeze.

I now have the SET audio amp to build, which I should be able to do while I am asleep.
I think I have a spare 6L6, which would be easier to drive than a 6CM5 in triode.

Patrick Turner.

In article , Patrick Turner
wrote:

John Byrns wrote:

In article , Patrick Turner
wrote:

John Byrns wrote:

In article , Patrick Turner
wrote:

I have seen no reference of your interpretive methodology in any
text books, and the text book methods to which I adhere to explain
it all nicely, and I don't have any intention of going right through
all that long and tortuous discussion again.

And I wouldn't ask you to, if you notice I am not disputing your method,
I am simply disputing your apparent claim that my method is invalid. I
would ask you for one favor though, could you cite some of the textbooks
that explain your method so nicely?

I would have a dozen on my shelf which explain radio theory sufficiently
well, including RDH4, and 11 others.

Ahh, the old weapons of mass destruction excuse, you have the RDH4 and 11
other text books, and yet you can't come up with a citation for your
method?

I won't have the same books as you have, but apart from RDH4,
I have Terman's Radio Engineering,
about 6 different dated copies of ARRL,
The british Communications Handbook, 5th Ed,
Phillips Radio Paractice, Essentials of Radio by Sluurzberb&Osterfield,
Applied Electronics by the staff of the Dept of Massacgusets insitute of
Technology,

Electrical and Electronic Engineering by John D Ryder,

Of those I have at least the RDH4, and Terman's Radio Engineering, plus
possibly one or two more, how about some page numbers where I can find an
explanation of your definition of the rate of increase of the attenuation
of a tank circuit around resonance?

and I am too lazy to copy out the titles of the other approximate 10 books
I have read on old fashioned electronics which all describe filters the same
way, but not the way you do.

Well I guess that about says it all, you are simply one of those old
fashioned blokes who can't change his ways to adopt newer and better
methods.

If you wanna uphold your methods, go write a book.

I suppose I could, but why, I am not a textbook author, and my methods are
not original with me, I am not nearly that clever. As I have said before
I took them straight out of the modern filter design textbooks, the books
on this subject have already been written by others, many times over, the
field is way too crowded. You need to expand your reading list beyond
those smelly old radio textbooks, the old blokes didn't know everything,
you might learn something new from some more up to date reading, if you
can even call it that.

All the books backing up what I am saying are on the shelves for you to read.

Page numbers please, if you can't cite page numbers it is nothing more
than BS! Don't worry, I'm not going to hold my breath waiting, or
anything like that.


Regards,

John Byrns


Surf my web pages at, http://users.rcn.com/jbyrns/